The present invention relates to a device operable to supply a force feedback to a physiological unit. The invention was developed with particular attention to a device operable to detect the configuration of a distal physiological unit and to supply a force feedback thereto.
Particularly, but not exclusively, the present invention relates to an advanced interface device between a human operator and a machine or computer, of the type operable to transmit to the machine information on the configuration of a distal physiological unit of the operator and to supply at least one part of the operator's body with a force feedback sensation.
Interface devices are known which enable an operator to interact with a machine or computer by transmitting information relating to the movement and the position of the hand or fingers. This type of interface device is used increasingly frequently in applications in the field of virtual reality and/or remote operation. These terms should be understood to mean the field of those applications in which events and situations involving man's interaction with the outside world are simulated, generally with the assistance of a computer, either for training purposes (flight or driving simulators for example), design purposes (products or industrial processes, architectural or town planning environments) or other recreational, didactic or humanitarian purposes (games, study programmes, communications systems for the disabled), or in sophisticated automation applications such as the remote control of a working robot in an environment which is inaccessible or dangerous to man.
In all these applications use is generally made of interface devices which enable an operator to interact, more or less fully and realistically, with virtual objects, represented by a computer, as though he was interacting directly with real objects.
One of these devices is described in Italian Patent Application N. T092A000941 by the same applicant.
However, the use of devices which allow only the movements and/or positions of an operator's hand and fingers to be detected is not entirely satisfactory in applications requiring a greater verisimilitude of the sensations produced during simulation, since these do not allow the operator an immediate and natural perception of the interaction with the objects, in effect of their solidity. In other words, with devices of the aforesaid type the virtual object always remains an abstract entity and the perception of interaction between man and object requires a conceptual effort on the part of the operator as, for example, the fact that the object has been gripped is visualised or indicated acoustically. A long period of training is required for an operator to be able profitably to use such an interactive system, and even after such training results may remain unsatisfactory.
It was thus felt necessary to develop interactive man-machine systems that appear more "natural", that is enable the interactive forces exerted on the operator to be as close as possible to those felt during normal gripping and manipulation of real objects. In particular, it was deemed necessary to reproduce the internal forces due to the gripping and manipulation of an object and the external forces due, for example, to its own weight.
A device of the aforesaid type is shown in International Patent Application WO 91/11775. This document describes and illustrates a device including a support in the form of a glove which can be fitted to the operator, and has position sensors for transmitting to a computer signals indicating the position of the fingers of the operator's hand, and also including a system of actuators, controlled by the computer and interacting with the tips of the fingers of the glove, operable to transmit force signals to the operator's fingers. In more in detail, the actuators include a plurality of electric motors and a series of tendons extending from the wrist, along the back and the palm of the hand and along the fingers to the finger tips. The computer controls the movement of the electric motors which, by tensing or relaxing the tendons, give a sensation of force to the operator's fingers, related to the conditions of contact with the virtual objects determined by the virtual reality program.
Such known devices involve a series of disadvantages which do not recommend their use in virtual reality applications in which the interaction between the hand and an object needs to be represented with sufficient verisimilitude. In fact, in known devices the force applied to the fingers of the operator's hand is determined by measuring the tension of the tendons. The considerable and unquantifiable friction between the tendons and the guide sheaths arranged on the support glove does not permit a measurement upstream of the transmission to be correlated sufficiently accurately with the force effectively exerted downstream of it.
In addition, the fact that the forces are exerted exclusively on the distal phalanges of the fingers does not permit correct simulation of any interactions with objects which involve other phalanges.
Finally, as devices of known type use flexible sheaths to guide the wires, which are supported by the glove and, in the final analysis, by the operator's own hand, the overall sensation is unnatural as the spurious forces necessary for the mechanical equilibrium of the sheath are added to the desired force on the operator's fingers.
All this contributes to falsifying the force sensation felt by the operator, differentiating it and distinguishing it from the natural sensations of interaction with real objects and thus meaning that a period of training and a conceptual effort are required to use known devices.